Development of the Cd-free CZTS Solar Cells with Subwavelength Nanostructure

The high efficiency of CuIn1-xGaxSe2 (CIGS) solar cell has been achieved a world-record efficiency cell of 20.3%. However, the cost of indium and gallium is expensive in mass production for terrestrial solar cells, and the CdS buffer layer has toxicity. Thus, alternative materials based on Cu-II-IV-VI4 solar absorbers have been developed; for example is Cu2ZnSn(S,Se)4 (CZTS). The main objective of this 3-year project is to investigate and develop Cd-feee CZTS solar cells and improve the efficiency by manipulating ZnO nanostructures. The influences of various processes on photoelectric characteristic of CZTS cells will be investigated in detail. In phase-I stage, we use the radio-frequency (RF) magnetron sputter and selenization systems to prepare high quality CZTS absorber layer. The aim of this stage is to develop pure CZTS thin films without secondary phases and realized the rectification characteristic. Meanwhile, CZTS absorber layer with double grading will be fabricated to increase the photo-voltage. The conversion efficiency of 5% is expected to be demonstrated. In phase-Ⅱstage, the CZTS solar cells with Cd-free buffer layer will be the main mission, and we expect the conversion efficiency of Cd-free solar cells can exceed 7%. This work is important in developing non-toxic, Earth-abundant elements thin-film solar cell. In phase-III stage, several techniques will be applied to fabricate low-dimensional ZnO-based nanostructures. The light-trapping ability may be enhanced under optimal process. The influence of surface morphologies on the light-trapping efficiency will be investigated by simulation results as well. The aim of this stage is to develop high efficiency CZTS solar cell with 10% efficiency. The achievements of this project can make substantial progress in developing CZTS solar cells providing environmental and manufacturing benefits.

Project ID:PB10111-0214
External Project ID:NSC101-2622-E182-004-CC2